1. Field of the Invention
The present invention relates to a semiconductor quantum effect device, and more particularly to an improved semiconductor device having negative differential resistance characteristics, and able to effect a high speed operation.
2. Description of the Related Art
Multibarrier tunneling is currently of great interest in the field of semiconductor quantum effect device research, primarily based on advances in crystal growth techniques, such as the hetero-junction growth technique. Accordingly, the research and development of a semiconductor device utilizing a tunneling effect has been flourishing. Above all, a resonant-tunneling device is intended for development as a high frequency oscillating device or a higher functional device and efforts in many fields are being devoted to their application.
In general, the above-described semiconductor device having a tunneling-effect is utilized to apply the potential in a conduction band or a valence band, the potential of which is determined univocally by what material is applied thereto. As is the case with the above-noted resonant-tunneling device, the improvement of electrical characteristics was dealt with by selecting an appropriate value of the shape and scale of potential configuration, such as the height or thickness of potential barriers.
According to the above-described prior art technology, when the shape and dimension of potential barriers are designed, enough freedom of design was not allowed so that limitation of design existed in order that the above-described electrical characteristics, for example, the ratio of peak current to valley current, that is, P/V ratio, or the peak current density, may be improved.
The present invention is devised to solve such a problem. Therefore, it is an object of the present invention to provide a semiconductor quantum effect device having negative differential resistance characteristics and provided with potential barrier layers which can be tunneled through to lead to a greater freedom of design.